Moulding processes

Question 1

Injection moulding process

Answer 1

granules of thermoset plastic are poured into a hopper, a rotating feed screw pushes the granules to build up frictional heat and pass along external heating bands. The liquid is forced into a mould by a hydraulic ram, it is cooled and the plastic hardens and then the mould opens and the product drops and the flash is trimmed

Question 2

Injection moulding pros, cons and uses

Answer 2

Pros - good for mass production, low unit costs, precision moulding, surface texture
Cons - high set up costs, expensive moulds to design and make
Uses - casting for electrical products, packaging, toys

Question 3

Injection moulding diagram

Answer 3

https://xcentricmold.com/wp-content/uploads/2019/05/injection-molding-machine-1024x412.png

Question 4

Blow moulding (preform) process

Answer 4

injection moulded pre-form is produced, the preform is clamped inside a mould with a hollow shape in shape of end product. It is heated and hot air is blown, the preform expands and is left to cool then the mould opens

Question 5

Blow moulding pros, cons and uses

Answer 5

Pros - intricate shapes, hollow shapes, thin walls to reduce weight and cost, mass production
Cons - high set up cost, expensive moulds to design and make
Uses - plastic bottles

Question 6

Blow moulding (parison) process

Answer 6

plastic if fed in granular form into a hopper and a large thread is turned to feed the granules through the heated area so it melts and the liquid is forced through a die to form a parison. The extruded parison is fed between a split mould and air is force3d into the mould giving the shape, its left to cool and the mould opens

Question 7

Blow moulding (parison) diagram

Answer 7

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMqm7VERp1x7sBxRIQcftMH4EIkTbQy1jLIUcgax78SsP9rRkqZIP4O8j0VEkNTsQn7z23PdFJKxKmPVpzNuhA0jGQfhkf92MtTxKXsAHldxBMVQ1pJjdck2IiQA3Lzt5UqhSil1w2itSp/w1200-h630-p-k-no-nu/ebm.jpg

Question 8

Vacuum forming process

Answer 8

a mould is designed with a draft angle and small air evacuation holes. A thermoplastic sheet is clamped above the mould and is heated from above. Once the polymer is soft the mould is raised and a vacuum cuases the air to be sucked out. It cools and solidifies and the mould is lowered and excess is trimmed off

Question 9

Vacuum forming pros, cons and uses

Answer 9

Pros - good for batch production, inexpensive, relatevely easy to make moulds, range of plastics - PET, HIPS, arcylic
Cons - accurate mould design needed to prevent webbing, large amounts of waste material produced, limited to thinner materials
Uses - yoghurt pots, blister packs, chocolate box inserts, packaging

Question 10

Vacuum forming diagram

Answer 10

https://hampshireplastics.co.uk/wp-content/uploads/2015/10/5420856.jpg

Question 11

What makes a good vacuum forming mould

Answer 11

rounded corners, tapered sides (draft angles so can be removed), vacuum holes allows plastic to be pulled into detailed shapes, airflow channels under mould allows for even vacuum

Question 12

Compression moulding process and what is it used for

Answer 12

a slug or charge of plastic is weighed out, the heated male and female moulds are pressed together. It is left to cure until the thermo-chemical reaction takes place. Once cured the part is removed and flash is trimmed
making compex shapes of thermoset plastic - plug sockets

Question 13

Extrusion moulding process

Answer 13

similar to injection mouldings. granules of plastic are poured into a hopper and a feed screw threads along the granules past the heating bands which melt the plastic. The molten polymers is forced through a die, froming a long tube-like shape. The extrusion is cooled and forms a solid shape and the shape of the die determines shape of tube

Question 14

Extrusion moulding pros, cons and uses

Answer 14

Pros - continous, high production volumes, low cost per unit
Cons - limited complexity of parts, uniform corss-section shape only
Uses - drain pipes, tubes

Question 15

Compression moulding diagram

Answer 15

https://upload.wikimedia.org/wikipedia/commons/b/bc/Compression_molding.svg

Question 16

Extrusion moulding diagram

Answer 16

https://i.ytimg.com/vi/S6XQrXfvbgc/hq720.jpg?sqp=-oaymwEhCK4FEIIDSFryq4qpAxMIARUAAAAAGAElAADIQj0AgKJD&rs=AOn4CLAXDNXjcEQuuKW161vaF6e13ZfARA

Question 17

Lamiation (lay up) plastic process

Answer 17

mould is prepared with a nonstick coating (release agent). Outer layers (resin) is rolled onto the mould and the fibre matting is pressed on top then resin is rolled over the matting to push inbetween fibres so even layers with no bubbles. Repeated until desired thickness. Vacuum bag can be used to compress layers together.

Question 18

Lamination (lay up) plastic uses

Answer 18

makes a fibre based materil soaked in resin which cures into a hard shell - boats, kayaks, roller carts

Question 19

Blow moulding (pre-form) process

Answer 19

an injection moulded pre-from is produced and the preform is clamped insidde a mould, with a hollow space in the shape of the end product. It is heated and air is blown into it. The preform takes the shape of the mould and the plastic is cooled. The mould opens and the product is ejected.

Question 20

Blow moulding (pre-form) pros, cons and uses

Answer 20

Pros - intricate shapes, hollow shapes, thin walls to reduce weight and cost, good for mass production
Cons - high set up costs, expensive to design and make moulds
Uses - plastic bottles

Question 21

Blow moulding (pre-form) diagram

Answer 21

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRhsO9jcyVb6Bi4C1tAiEPqiB-XHG-Aa48gWA&s

Question 22

Rotational moulding process

Answer 22

the mould opens and is filled with powered polyethylene and closed, the moulds are usually manufactured from alumininm on CNC machine. The mould is heated at the same time is mould rotates in all axis so the powder is forced against the wall of mould. Cool air is blown around mould and mould cools slowly and product is removed.

Question 23

Rotational moulding procs, cons and uses

Answer 23

Pros - investment on equipment and tooling is less that blow moulding, no seams, uniform wall thickness, metal inseys can be added
Cons - lower volume production, labour intensive
Uses - buckets, basketballs, oil drums, traffic cones

Question 24

Rotational moulding diagram

Answer 24

https://lirp.cdn-website.com/dce00838/dms3rep/multi/opt/ROTOMOLDED-PROCESS-STEPS-640w.png